In (REF ), (REF ), and (REF ) we use the facts that for \(i=1\)  the system model is not a function of \(\gamma \) , and in S-K
coding scheme \(X_{(1)i}\) , \(X_{(2)i}\) , and \(Y_i\)  are independent of \(Y^{i-1}\)  [1]}. The mutual information for this model can be written as,
\(I_{S-K} \left( {M_{\left( 1 \right)} ,M_{\left( 2 \right)} ;Y^n } \right) &= h\left( {Y^n } \right) - h\left( {Y^n \left| {M_{\left( 1 \right)} ,M_{\left( 2 \right)} } \right.} \right) \\&= \frac{1}{2}\ln \left( {\left( {2\pi e} \right)^n \left| {{\bf {\Sigma }}_{Y^n } } \right|} \right) - \frac{1}{2}\ln \left( {\left( {2\pi e} \right)^n \left| {{\bf {\Sigma }}_{W^n } } \right|} \right) \\&= \frac{1}{2}\ln \left| {{\bf {\Sigma }}_{Y^n } } \right|\) 
